Fuel injection device for internal combustion engines



E. SCHAEREN Aug. 7, 1934.

FUEL INJECTION DEVICE FOR INTERNAL COMBUSTION ENGINES Filed Nov. 25. 1931 Vivir@ WAV/.151.

Il I Patented Aug. -7, 1934 UNITED STATES FUEL INJECTION DEVICE FOR INTERNAL COMBUSTION ENGINES Ernst Schaeren, Solothurn, Switzerland Application November .25, 1.931, Serial No. 577,369

2 Claims.

The invention relates to an airless fuel injection device comprising a driven piston and a loaded counter piston in the same pump cylinder, suction and pressure slots in said cylinder,

5 the pressure slots being connected with a fuel injection valve of the usual fuel opened-springclosed type, mounted at or on the cylinder. Inr

such arrangements the accumulator spring has to be made suitable to overcome the opening pressure of the fuel injection valve spring. Strong springs and robust pump-members had to be used.

On the other hand for idling load i. e. for small1 fuel quantities the engines were often missing as l5 the tubing for high pressure accumulated a ceramount of fuel, i. e. if the fuel quantity for idling was not sufficient to equalize the difference of pressure between opening and closing pressure of the valve needle, the latter remained closed and reopened but on the next or on one of the following injections.

To overcome these disadvantages the driven piston is made larger in diameter by a certain amount than the counter piston and this amount lies in the limits of 100 to 200 per cent of the diameter of the counter piston. After the injection period the driven piston is moving towards the/inner dead center where the pump chamber is connected to the fuel inlet pipe and thereby re- I v lieved. On the outward stroke a vacuum is created in the pump chamber determined by the diiference in area of the 2 pistons. When the steering groove of the driven piston registers with the delivery port of the pressure pipe, a decrease in pressure occurs in the latter, rendering a higher injection pressure possible as will be explained later on.

Referring to the drawing the single figure is a vertical section through the fuel injection device.

The preferred form of the device is the only embodiment of 4the invention illustrated and will now be described in detail but without implication of limitation beyond the scope of the invention as set forth in the claims.

a represents the pump cylinder for the driven piston b and the counter piston c. d is the pump chamber into which the fuel is flowing through the pipe e. h and i are the drive members for the driven piston b. lc is the pressure channel of the pump leading by means ofthe pipe m to valve casing o mounted on lthe cylinder n. pis the injection needle which is under the pressure of the spring r. The accumulator spring q is thrusting against the counter piston c. The driven piston 55. b has an annular groove w which is 'in connection (Cl. 10S-154) wh the pump chamber d by means of the chanl n 1J.

The top of the pump plunger b' uncovers the fuel inlet port on the downward stroke and the pump chamber d is charged with fuel. During 50 the upward stroke of the plunger b the fuel is put under increased pressure. A soon as the annular groove w registers with the delivery port 7c the fuel is delivered from the pump chamber d to the injection valve p. When the pump plunger'b 05 reaches the end of its upward stroke, port u register with the fuel intake port thus relieving the pressure in the pump chamber. During the next downward stroke of the pump plunger a vacuum is created in the pump chamber d as the plunger b is larger in diameterA than the plunger c. As soon as the groove w registers on the following downward movement of the pump plunger with the port lc the pressure in the line m is relieved and a reduction in pressure created. The purpose of relieving the pressure in line m is to attain a greater difference in pressure between pump chamber d and pressure line m. This greater difference of pressure is required for attaining a greater opening pressure for the fuel injection valve in order to avoid the missing of the engine, when idling or alternatively for reducing the required working pressure on the pump plunger thus reducing the stress on the pump members.

In case the pump plunger b and the accumulator plunger c have equal diameters the operation to get the required opening pressure for the needle p is as follows: The valve needle p is closed by the spring r which is compressed to about 300 atms.; the same pressure of 300 atms. exists after closing of said valve needle p in the pressure line m, which is full of fuel; if the pressure in the pump chamber d is for instance 340 atms., the moment the groove w registers with the delivery port k, the pressure line m is instantly exposed tofthis increased pressure of 340 atms. i. e. there exists now a difference in pressure of 40 atms. between pump chamber d and pressure line m. This causes in the pressure line m a. pressure wave having a speed u which can be calculated by the formula:

u=p Y J p=pressure difference (40 atms.) g=9,81 mkZ/sec. 2 c=constant J=speciflc weight of liquid. K This wave is transmitted up t0 the valve needle 1,10

p. where it is reected. As during this operation the accumulator plunger c is in motion, i. e. delivers fuel into the pressure line m-there is tor a certain extent a stream now into the line 'mfthe increased pressure of 340 atms. remains in the pressure line m and the kinetic energy of the liquid column, which has a speed of in the line mis transformed into potential energy as this speed u of the pressure wave is reduced to naught, after the port k has been closed again by the pressure plunger b. The increase in pressure p attained thereby is calculated again by the formula:

u=pY J i. e. this increase is 40 atms. also, added to 340 atms. already in the pressure line m, makes 380 atms., which is about the required opening pressure for the needle valve p.

Assuming now the pressure in the pump chamber is but 330 atms. the difference of pressure between pump chamber b and pressure line m is then 30 atms. resulting in an opening pressure of 30M-60:36!) atms. at the needle valve p.

According to the invention the diameter of the pump plunger b is made larger in diamer than the one of the accumulator plunger; a reduction of pressure in the pressure line m is attained when the groove w registers with the port lc on the downward stroke of the pump plunger. Assuming this decrease in pressure is 20 atms., i. e. from 30G-280 atms. in the pressure line, a difference in pressure of 50 atms. will now exist between pump chamber b and pressure line m for a delivery pressure of 330 atms. in the pump chamber b, when the groove w registers with the port 7c; this results in an opening pressure of 280+l00=380 atms.

Assuming on the other hand the same condirooaooi tions of pressure in the pump chamber a higher opening pressure at the Valve will result and an improvement with respect to the idling conditions of the engines is obtained in so far as by ncreasing the opening pressure for the valve needle no more missing of the engine will take place.

What I claim is:

i. Airless fuel injection device for internal' thereby relieving the pump chamber, a fuel delivery port in said pump body a certain distance apart from the fuel inlet port, towards the outer dead center, said fuel delivery port being adapted to register with said groove of the pump plunger on its outward stroke, in this moment creating a decrease of pressure in said pressure line.

2. Airless fuel injection device for internal combustion engines, comprising in combination a spring loaded counter plunger, a pump plunger, larger in diameter by 100 to 200 per cent than the counter plunger, a pump body, a pump chamber, a fuel inlet port in said pump body, a groove in the pump plunger, an axial channel vin the pump plunger, connecting 'said groove to the pump chamber, said groove being adapted toregister with the fuel inlet port in the inner dead center of the pump plunger, thereby relieving the pump chamber, a fuel delivery port in said pump body a certain distance apart from the fuel inlet port towards the outer delivery port being adapted to register with said groove of the pump plunger on its outward stroke, in this moment creating a decrease of pressure in said pressure line.

ERNST SCHAERM.

dead center, said fuel. 

